Process for printing a carrier material

ABSTRACT

In a printing method and system for production of a print image on a carrier material, a print carrier is provided, a surface of which is charged with water vapor at locations corresponding to structures of the print image to be printed. Water vapor is condensed at these locations as a film of water. Ink is applied to the surface, the ink adhering to non-wetted locations and not being accepted by the wetted locations. The ink from the non-wetted locations is printed onto the carrier material.

BACKGROUND OF THE INVENTION

The invention relates to a printing method for producing a print imageon a carrier material, in which a print carrier is provided whosesurface is charged with water vapor in a manner corresponding to thestructure of the print image to be printed.

In known printing methods, such as the offset printing method, partialprinting regions corresponding to the print image to be printed areprovided on the surface of a print carrier, e.g. a print plate, aprinting strip or a print master, which regions are inked with inkduring the print process and subsequently print the carrier materialwith the ink. Various methods are known for the formation of thesepartial printing regions. For example, in the direct imaging method ofthe company Heidelberger Druckmaschinen, a print master is produced on asilicon-coated film by partially burning away the silicon layer, and thesilicon-free locations accept the ink during the print process and printthe carrier material. In another known method, hydrophobic andhydrophilic regions corresponding to the structure of the print image tobe printed are produced on the print carrier. Before the application ofink to the print carrier, a thin film of moisture is first applied tothe print carrier using application rollers or, respectively, sprayingsystems, which film wets the hydrophilic regions of the print carrier.Subsequently, using an ink roller, ink is applied to the surface of theprint carrier, which however uses exclusively the regions not coveredwith a film of moisture. After the inking of the print carrier, theinked print image is finally transferred to the carrier material.

From U.S. Pat. No. 3,072,049 and U.S. Pat. No. 2,002,815, printingsystems are known that respectively operate according to a printingmethod in which in order to produce the thin film of moisture on thesurface of the print carrier, instead of using application rollers orspraying systems water vapor is applied to the hydrophilic regions ofthe print carrier. Here as well, the surface of the print carrier, whichis charged with water vapor, is divided into hydrophobic and hydrophilicregions corresponding to the structures of the print image to beprinted.

The printing methods described above all have in common that a printcarrier has to be used on a surface of which raised and flat regions, orhydrophobic and hydrophilic regions, are provided corresponding to thestructures of the print image to be printed.

SUMMARY OF THE INVENTION

An object of the invention is to provide a flexible printing method inwhich the print image to be printed can be modified in a simple manner.

This object is achieved by means of a printing method for production ofa print image on a carrier material where a print carrier is provided, asurface of which is charged with water vapor at locations correspondingto structures of the print image to be printed. Water vapor is condensedat the locations corresponding to the structures of the print image as afilm of water. Ink is applied to the surface, the ink adhering tonon-wetted locations and not being accepted by the wetted locations. Theink is printed from the non-wetted locations onto the carrier material.

By means of the invention, a printing method is provided in which thesurface of the print carrier is selectively and partially charged withwater vapor in such a way that a partial water film that yields theprint image forms on the surface. Given the use of this printing method,the use of a print carrier on whose surface hydrophilic and hydrophobicregions are provided can be dispensed with, so that additionaloperational steps are omitted. In place of the chemically pre-treatedprint carrier, the printing method with selective use of water uses aprint carrier with a uniform surface onto which the film of wateryielding the print image is applied. By this technique, it is possibleto modify the print master within a print process, so that the printingmethod operates with very high flexibility.

In a further embodiment of this printing method, the use of anintermediate carrier, for example a rubber sheet or a roller with arubberized surface, is additionally proposed, which is adapted to thedifferent carrier materials used.

For the selective and partial charging of the surface of the printcarrier with water vapor, in a development of the method a strip offabric moistened with water is arranged opposite the surface of theprint carrier, and is selectively heated at locations corresponding tothe print image, using a source of radiation, e.g. a laser with adeflection and focusing optics, high-temperature lamps or laser diodearrays, and/or a source of heat, such as heating elements, thermocombsor microwave elements. In this way, on the side of the strip of fabricfacing the surface of the print carrier, water will emerge as steam atthe correspondingly heated locations, and will condense on the surfaceof the print carrier. In order to moisten the strip of fabric withwater, it is guided in a continuous movement e.g. through a rollersystem and/or a spray unit. Of course, it is also conceivable to movethe strip of fabric through a water bath, whereby the strip of fabricabsorbs water due to capillary action.

In a further embodiment of the method, instead of a moistened strip offabric, a vaporization unit with a supply of water is arranged oppositethe surface of the print carrier. The vaporization unit has a largenumber of recesses filled with water in which at least one heatingelement is respectively provided that can be actuated independent of theother heating elements. By the application of impulses, the heatingelements are selectively activated so that the water located in therecess is vaporized and condenses on the print carrier locatedthereabove. By varying the magnitude of energy supplied, the quantity ofvapor can be modified in a defined manner. In addition, it is possibleto organize the film of water that arises in punctiform manner in itsthickness.

It is particularly advantageous if the surface of the print carrier ischarged with vapor in grid fashion and row-by-row, whereby a continuousprocessing of the print data driving the print machine is enabled.

In the following, the invention is explained in more detail on the basisfor the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of a unit for selective and partialvaporization of the surface of a print carrier;

FIG. 2 shows a printing system in which the unit according to FIG. 1 isused; and

FIG. 3 shows a second embodiment of a unit that can be used for theselective and partial vaporization of the surface of the print carriershown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 describes a first embodiment of a vaporization system 70 for theselective vaporization of the printing strip 72 of a printing means 74(cf. FIG. 2). The vaporization unit 70 has a strip of fabric 76 that isdriven in the direction of motion of the printing strip 72 and isarranged in parallel to the printing strip 72 at a slight distance. Thisstrip of fabric is continuously moistened with water by means of aroller system having rollers 201 and 202, or alternatively the strip offabric is continuously moistened with water by means of a spray unit 204emitting the spray 205. On the side of the strip of fabric 76 facingaway from the printing strip 72, a heating unit (not shown) is providedthat extends approximately over the entire width of the printing strip72, transverse to the direction of motion thereof. This heating unit hasa plurality of sources of radiation 78 arranged next to one another in arow in the longitudinal direction of the heating unit which sources ofradiation can be activated selectively and independent of one another.

FIG. 2 shows a schematic view of the printing unit 74 in which the firstembodiment of the vaporization unit 70, specified in FIG. 1, is used.The printing unit 74 has a driven conveyor roller 80 that rotates in theclockwise direction and is shown at left in FIG. 2, as well as a printerroller 82 arranged at approximately the same height and shown at theright in FIG. 2, whose axis runs parallel to the axis of the conveyorroller 80. A deflecting roller 84 is provided approximately centrallypositioned to the conveyor roller 80 and the printer roller 82,underneath these rollers and running parallel to them. The printingstrip 72 is led over the conveyor roller 80, the printer roller 82 andthe deflecting roller 84.

The vaporization unit 70 described in FIG. 1 is arranged above theconveyor roller 80 and the printer roller 82, approximately in thecenter between these. In the region of the printer roller 82, an inkingstation 86 is provided after the vaporization unit 70, seen in thedirection of transport of the printing strip 72. This inking station 86has an inking roller 88 that is applied to the printing strip 72 and ispre-stressed against the printing roller 82. A supply roller 90, whichis applied under pre-stressing to the inking roller 88 and which dipsinto an ink container 92 filled with ink, supplies the inking roller 88with ink. The transfer printing location 94 is provided immediatelyafter the inking station 86, at which location a counter-pressure roller96 is pre-stressed against the printing roller 82, applied to theprinting strip 72 under pre-stressing. The counter-pressure roller 96and the printer strip 72 applied to the printing roller 82 form atransport gap 98 through which the carrier material 100 is moved.

Finally, in the region of the deflecting roller 84 a cleaning unit 102is arranged, seen in the direction of transport of the printer strip 72.The cleaning unit 102 has a stripper lip 104 applied to the printerstrip 72 under pre-stressing and a subsequently arranged cleaning brush106, which serve for the removal of water and residual ink on theprinting face of the printer strip 72.

As soon as the printer unit 74 is activated, the radiation sources 78 ofthe heating unit begin to heat the strip of fabric 76, which ismoistened with water, in selective and partial fashion, whereby thewater stored in the strip of fabric 76 is vaporized and condenses ontothe side of the printing strip 72 facing the strip of fabric 76. In thisway, a partial film of water that reproduces the print image is formedon the surface of the printing strip 72. The printing strip 72,moistened in this way, is supplied to the inking station 86, in whichthe inking roller 88 applies ink to the surface of the printing strip72. The regions not wetted with water are thereby inked, while the waterin the regions wetted with water prevents an inking of these regions.After the inking of the printer strip 72, the inked segment of theprinter strip 72 moves into the transfer printing location 94, in whichthe inked print image is printed directly on the carrier material 100 bymeans of the effect of the counter-pressure roller 96.

FIG. 3 shows a second embodiment of a vaporization unit 120 that can beused in place of the vaporization unit 70 in the printing unit 74 shownin FIG. 2. The vaporization unit 120 has a heating rail 122 extendingtransverse to the direction of transport of the printing strip 72, overthe entire width thereof. The heating rail 122 has in its longitudinaldirection a plurality of cylindrical recesses 124 arranged next to oneanother in a row, respectively having a heating element 126 at theirclosed frontal side, and the respective open frontal side of which facesthe printer strip 72. By means of selective activation of the heatingelements 126, the water located in the respective recess 124 is heatedso strongly that it vaporizes and condenses on the side of the printingstrip 72 facing the heating rail 122, so that a partial film of waterreproducing the print image is formed. Subsequently, the strip 72 wettedin this way, as already described above, is transported in the same waythrough the inking station 86 and the transfer printing location 94 inorder to print the carrier material 100.

Although various minor changes and modifications might be proposed bythose skilled in the art, it will be understood that our wish is toinclude within the claims of the patent warranted hereon all suchchanges and modifications as reasonably come within our contribution tothe art.

What is claimed is:
 1. A printing method for production of a print imageon a carrier material, comprising the steps of:arranging a vaporizationunit with a water supply opposite a surface of a print carrier, thevaporization unit having a plurality of recesses with closed bottomsfilled with water in which at least one heating element is respectivelyprovided at the closed bottoms and spaced from an exit aperture of eachrecess; selectively heating the heating elements corresponding to theprint image; charging the surface of the print carrier with water vaporfrom the vaporization unit at locations corresponding to structures ofsaid print image to be printed; condensing water vapor at saidlocations; applying ink to the surface of the print carrier, the inkadhering to non-wetted locations and not being accepted by the wettedlocations; and printing the ink from the non-wetted locations onto thecarrier material.
 2. The printing method according to claim 1 in whichthe surface of the print carrier is charged with vapor row-by-row, inthe manner of a grid.
 3. A printing system, comprising:a movable printcarrier, a surface of which is wetted with a film of water; avaporization unit arranged near the surface of the print carrier whichcharges the surface with water vapor corresponding to structures of aprint image to be printed such that a partial film of water thatreproduces the print image forms on the surface of the print carrier,the vaporization unit comprising a heating rail extending transverse toa direction of motion of the print carrier, having a plurality ofrecesses with closed bottoms filled with water, and a heating elementbeing provided in each recess at the closed bottoms and spaced from anexit aperture of each recess; and an inking station arranged near thesurface of the print carrier after the vaporization unit in a directionof motion of the print carrier for application of ink to the surface. 4.A printing method for production of a print image on a carrier material,comprising the steps of:providing a vaporization unit with a watersupply arranged opposite and beneath a surface of a print carrier, thevaporization unit having a plurality of recesses with closed bottomsfilled with water in which at least one heating element is respectivelyprovided at the closed bottoms and spaced from an exit aperture of eachrecess, the heating elements being selectively heated corresponding tothe print image; charging the surface of the print carrier with watervapor rising from the recesses at locations corresponding to structuresof the print image to be printed; condensing water vapor at saidlocations; applying ink to the surface of the print carrier, the inkadhering to non-wetted locations and not being accepted by the wettedlocations; and printing the ink from the non-wetted locations onto thecarrier material.
 5. A printing system, comprising:a movable printcarrier, a surface of which is wetted with a film of water; avaporization unit with a water supply arranged opposite and beneath asurface of the print carrier, the vaporization unit having a pluralityof recesses filled with water in which at least one heating element isrespectively provided at closed bottoms and spaced from an exit apertureof each recess, the heating elements being selectively heatedcorresponding to the print image; a surface of the movable print carrierbeing wetted with a film of water as a result of rising vapor; and aninking station arranged near the surface of the print carrier after thevaporization unit in a direction of motion of the print carrier forapplication of ink to the surface.
 6. A printing method for productionof a print image on a carrier material, comprising the stepsof:arranging a strip of fabric moistened with water arranged opposite asurface of a print carrier, and selectively heating the strip of fabricusing a radiation source at locations corresponding to structures of theprint image to be printed; charging the surface of the print carrierwith water vapor from the strip of fabric at said locations; condensingwater vapor at said locations as a film of water; applying ink to thesurface of the print carrier, the ink adhering to non-wetted locationsand not being accepted by the wetted locations; and printing the inkfrom the non-wetted locations onto the carrier material.
 7. The printingmethod according to claim 6 in which the strip of fabric is moistenedwith water in a continuous movement.
 8. The printing method according toclaim 6 wherein the strip of fabric is moistened with water by use of aroller system.
 9. The printing method according to claim 6 in which thestrip of fabric is moistened with water by use of a spray unit.
 10. Theprinting method according to claim 6 in which the surface of the printcarrier is charged with vapor row-by-row, in the manner of a grid.
 11. Aprinting system, comprising:a movable print carrier, a surface of whichis wetted with a film of water; a vaporization unit arranged near thesurface of the print carrier which selectively charges the surface withwater vapor corresponding to structures of a print image to be printedsuch that a partial film of water that reproduces the print image formson the surface of the print carrier, said vaporization unit comprising astrip of fabric that is moistened and is led past the surface of theprint carrier at a slight distance, and that is selectively heated inpartial fashion by means of a source; and an inking station arrangednear the surface of the print carrier after the vaporization unit in adirection of motion of the print carrier for application of ink to thesurface.
 12. The system according to claim 11 wherein a cleaning unit isarranged before the vaporization unit in the direction of motion of theprint carrier for cleaning the surface of the print carrier of residualwater and ink.
 13. The system according to claim 11 in which the printcarrier is guided via at least two rollers.
 14. The system according toclaim 13 wherein at least one of the at least two rollers is driven. 15.The system according to claim 11 in which the print carrier comprises adriven printer roller.
 16. The system according to claim 11 wherein thesource comprises a radiation source.
 17. The system according to claim11 wherein the source comprises a heat source.
 18. A printing system,comprising:a movable print carrier, a surface of which is wetted with afilm of water; a vaporization unit comprising a strip of materialmoistened with water and which is selectively heated with a radiationsource adjacent the strip of material arranged near the surface of theprint carrier which charges the surface with water vapor correspondingto structures of a print image to be printed such that a partial film ofwater that reproduces the print image forms on the surface of the printcarrier; and an inking station arranged near the surface of the printcarrier after the vaporization unit in a direction of motion of theprint carrier for application of ink to the surface.